Routine AC unit preventive maintenance

If you feel that the AC covers are starting to get brittle, it is time to replace them before they blow off.
The alternative is to cover them with fiberglass cloth and resin, like I did to make sort of a permanent repair.

Pretty much as others have mentioned. Get on the roof and pull the covers to clean out the exposed side yearly (part of my dewinterizing routine). Interior coil I also clean every couple of months by vacuuming. I'm probably overdoing the interior coil effort but I want to avoid having to use an liquids and a deep cleaning. Stuff does get past or thru the filters.

Check the condenser coil for damage from hail and stuff, if fins are folded/ damaged, order fin comb off Amazon https://www.amazon.com/Diversitech-T-400-Tool-Super-Comb/dp/B004493K96/ref=sr_1_9?ie=UTF8&qid=1498616289&sr=8-9&keywords=fin+comb

Snug down do not OVER tighten the four hold down bolts on the inside.

Clean coils twice a year, filters monthly...but we fulltime. Never have oiled motors. Our 2 15,000 BTU Coleman heat pumps, the front unit has been changed out due to compressor failures three times, the rear unit has only had a hard start capacitor installed. Bought the RV new in December 2005, units basically run whenever we are in it.

Cleaning the coils will get you up on the roof removing the covers where you'll find any birds nests that have been built. Get the foaming cleaner, it pushes the dirt out.

I oil the motors twice a year and clean the coils once a year.